Suppress pipeline output in Context / Describe

Any pipeline output from Describe and Context blocks is now discarded, just as it already was for It blocks.
Coverage Output Update

Common parent paths are now automatically stripped from the File column of the on-screen coverage output (though the full paths are still available in the -Passthru output).  This keeps deep folder structures from taking up all of the on-screen space, sometimes removing the Command column entirely.
Common parent path based on all coverage files, not just missed

If you're analyzing coverage on, for example:

    Folder\Subfolder1\File.ps1
    Folder\Subfolder2\File.ps1

Where the file names are not unique, but the paths are, in the previous commit you'd just see 'File.ps1' if only one of the files contained missed commands.  In this commit, you'll see 'Subfolder1\File.ps1'.  The "common parent folder" check is done against the whole list of analyzed files, rather than just the files that happened to have missed commands.
Merge pull request #155 from dlwyatt/SuppressTestOutput

Suppress pipeline output in Context / Describe
Merge pull request #156 from dlwyatt/CoverageOutputUpdate

Coverage Output Update
Updating changelog
Allowing Pester to analyze its own coverage

Re-added the plumbing that allows Pester to do coverage analysis of its own code with a closer to accurate result.  This is extremely slow, though, so I'll probably just keep this branch separate and rebase it as necessary.